Spectral distribution of steady-state photoconductivity in amorphous As2Se3

The spectral distribution of steady-state photoconductivity has been examined for a series of bulk and evaporated samples of amorphous As₂Se₃. All bulk samples, irrespective of preparation technique or sample treatment, show a distinct shoulder in the photocurrent spectral distribution at energies near 1.4 eV. This feature is interpreted as spectroscopic evidence for the existence of a well-defined defect level in the gap of amorphous As₂Se₃. Evaporated As₂Se₃ films do not show any structure in the spectral response.     

Reversible photo-induced volume changes in evaporated As2S3 and As4Se5Ge1 films

Reversible photo-induced volume changes have been observed accompanying reversible optical absorption edge shift produced by successive cycles of band gap illumination and annealing for well-annealed evaporated As₂S₃ and As₄Se₅Ge₁ films. The As₂S₃ film shows an increase in its volume by illumination, while As₄Se₅Ge₁ film shows a decrease. Qualitative discussion has been given in connection with pressure-induced optical constant change.     

Kinetics of photo‐darkening and self‐bleaching in amorphous As2S3 and As2Se3 thin films

The kinetics of photo‐darkening of amorphous As₂S₃ and a‐As₂Se₃ thin films follows a single exponential, but the magnitude and the rate of the process is higher in case of As₂S₃. The kinetics of self‐bleaching (dark relaxation) in advance photo‐darkened state follows a stretched exponential (SRE) with different stretching parameter for a‐As₂S₃ and a‐As₂Se₃. Within the J. C. Phillips approach we suppose that photo‐darkening in amorphous As₂S₃ films is, to some extent, accompanied by changes in short‐range order interactions, while photo‐darkening of amorphous As₂Se₃ is accompanied rather by changes in Coulomb interactions. The self‐bleaching process reduced the magnitude of photo‐darkening up to 45% and 60% for amorphous As₂S₃ and As₂Se₃ films, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ultrafast non-linear optical properties of Ge20As25Se55 chalcogenide films

The non-resonant third-order non-linear optical properties of amorphous Ge₂₀As₂₅Se₅₅ films were studied experimentally by the method of the femtosecond optical heterodyne detection of optical Kerr effect. The real and imaginary parts of complex third-order optical non-linearity could be effectively separated and their values and signs could be also determined, which were 6.6 × 10⁻¹² and −2.4 × 10⁻¹² esu, respectively. Amorphous Ge₂₀As₂₅Se₅₅ films showed a very fast response in the range of 200 fs under ultrafast excitation. The ultrafast response and large third-order non-linearity are attributed to the ultrafast distortion of the electron orbitals surrounding the average positions of the nucleus of Ge, As and Se atoms. The high third-order susceptibility and a fast response time of amorphous Ge₂₀As₂₅Se₅₅ films makes it a promising material for application in advanced techniques especially in optical switching.     

Photoinduced absorption edge shift of As20Se60Tl20 films

As₂₀Se₆₀Tl₂₀ bulk material was prepared firstly then thermal evaporation method was used to prepare As₂₀Se₆₀Tl₂₀ films. Illumination effect at room temperature for the mentioned films has been studied within the homogeneous glass-forming region. The prepared film samples were amorphous, this is depicted by X-ray chart. Optical properties have been studied using spectrophotometric measurements. The absorption edge was shifted to shorter wavelengths due to light exposure or photobleaching effect. It was found that the extinction coefficient and the optical band gap have opposite character after illumination.     

Photoinduced phenomena in mAs2S3·nAs2Se3 amorphous films and their application in micro-optics technology

Photoinduced phenomena, such as photodarkening, photorefraction, and photodissolution, were studied in different compositions of three-component mAs₂S₃·nAs₂Se₃ amorphous films. The main emphasis was on the effect of photoinduced change of dissolution rate since this effect is the basis of many applications of amorphous chalcogenide films. The results of the investigation were compared with photoinduced effects in binary As₂S₃ and As₂Se₃ films. Advanced micro-optical devices: micro-lens and micro-mirror arrays, diffractive gratings, and photonic bandgap crystals, based on three-component amorphous films which possessed optimal photodissolution characteristics were developed. The primary parameters of the micro-optical devices developed are discussed.     

Photo-induced changes in the infrared vibrational spectrum of evaporated As2S3

Photo-induced changes in the infrared spectrum of amorphous, evaporated As₂S₃ films are described. The results are interpreted in terms of the photopolymerization of As₄S₄ molecular units and sulfur chains into an As₂S₃ glassy network. The role of photo-induced charged states in the polymerization process is discussed.     

Experimental study and configurational-coordinate model for photo-induced effects in amorphous As2Se3 films

The optical absorption of As₂Se₃ thin films is studied in the UV–VIS spectral range and the value of the optical energy gap is determined. The effect of photo-irradiation on the optical absorption and transmission of thin film samples is also investigated. The optical energy gap was found to decrease with photo-irradiation time. The results of photo-irradiation are discussed in correlation with the structural aspects of As₂Se₃. A model is proposed to account for the structural changes, resulting from photo-irradiation, causing the decrease of the energy gap. The effect of γ-radiation on the optical absorption of As₂Se₃ thin films was studied also and no detectable effect on the value of the optical energy gap was observed.     

The reversible photostructural change studied by ESR of Mn2+ in As2Se3 films

The reversible photostructural change is studied from a microscopic point of view using ESR of Mn²⁺ doped in As₂Se₃ films. It is observed that the hyperfine structure constant changes reversibly corresponding to the reversible optical absorption edge shift. The result is explained in terms of increasing randomness by photoirradiation.     

Photoelectron spectra of As4S3, P4S3, P4Se3 and As4O6

The He(I) UV photoelectron spectra of As₄S₃, P₄S₃, P₄Se₃ and As₄O₆ are reported in this paper. The spectra of As₄S₃ and the isostructural molecules P₄S₃ and P₄Se₃ comprise seven broad but clearly defined peaks, whilst the spectrum of As₄O₆ consists of six peaks and two shoulders. By comparing the spectra with one another and with the photoelectron spectra of other arsenic and phosphorus compounds, the character and symmetry species of the highest-energy occupied molecular orbitals of the molecules have been assigned.     

Infrared properties of AsχTe1−χ glasses

Infrared reflection and transmission measurements in As_χTe_1?χ glasses (45?×?55) show well-defined Gaussian vibrational absorption peaks. Comparisons with spectra observed in crystalline and glassy As₂S₃ and As₂Se₃ indicate that the local order in As_χTe_1?χ glasses is not like that found in crystalline As₂Te₃, but rather it consists primarily of AsTe₃ pyramids which are probably linked together in a fashion similar to that found in As₂S₃ and As₂Se₃.     

Photoplasticity of As2Se3 films investigated with combined nanoindentation and AFM methods

Thin As₂Se₃ amorphous chalcogenide films have been studied by nanoindentation and atomic force microscopy in darkness and under illumination by band-gap light. The combination of these two methods has been used to study the peculiarities of the photoplastic effect in amorphous semiconductors. It has been shown by multiple loading indentation experiments that a non-linear mechanism of the formation of the strain response is realized in the As₂Se₃ films subjected to the combined action of light and external mechanical loading. We have observed that light illumination alters the internal friction of the films and their shear modulus. These observations have been considered in the frame of the two-phase model of chalcogenide glasses. Some arguments in favor that the self-organization processes take place in the structure of irradiated film are given.     

非晶态As-Se二元系短程结构的EXAFS研究

用12kW转靶X射线衍射装置测定了非晶半导体a-As₂Se₃,a-AsSe以及a-As_0.05,Se_0.95的k吸收EXAFS,a-As₂Se₃经T≤T_g(玻璃转变温度)的不同温度处理后,亦进行了测定。由获得的径向结构函数分析表明:尽管a-As₂Se₃的短程结构与晶态c-As₂Se₃十分相似,但经过低于T_g的退火处理后,其径向结构函数发生了一定的变化。熔态淬火制备的a-As₂Se₃块体亦发生结构弛豫。此外,在非晶态As-Se二元系中随As含量的变化,材料的近程结构亦不同。 关键词：     

硫系非晶半导体薄膜中的超快光 Kerr效应

利用飞秒激光超外差光Kerr(OHD-OKE)技术研究了As₂S₃, As₂Se₃, GeS₂, GeSe₂, Ge₂₀As₂₅S₅₅, Ge₂₀As₂₅Se₅₅, Ge₁₀As₄₀S_{20关键词： 全光开关 硫系非晶半导体薄膜 飞秒激光超外差光Kerr(OHD-OKE) 三阶非线性}     

Raman spectra of As4S4 polymorphs: Structural implications for amorphous As2S3 films

Raman-scattering spectra of α-As₄S₄ and β-As₄S₄ have been determined at 300 and 10 K. Although similar in overall aspect, the spectral signatures of the two polymorphs are clearly distinct. We have made a careful comparison of these first-order crystal line spectra to the sharp features reported in the Raman spectra of freshly-deposited films of amorphous As₂S₃. Prior proposals for the presence of As₄S₄ molecules in the unannealed films are supported by these comparisons, but recent contentions that actual microcrystals of β-As₄S₄ are present in the as-deposited material are clearly contradicted by the absence of any of the lattice-phonon lines which are prominent in the crystals at frequencies below 70 cm^-1.     

High-frequency dielectric properties of glassy As2Se3

The dielectric properties and the ac conductivity of glassy As₂Se₃ have been obtained for a wide frequency range at temperatures between 80 and 300 K. The results are described in terms of a non-Debye-type dielectric response due to a coupling of a polarization response to structural modes.     

Femtosecond optical Kerr effect study of Ge10As40S30Se20 film

The results of the femtosecond optical heterodyne detection of optical Kerr effect at 805 nm with the 80 fs ultrafast pulses in amorphous Ge₁₀As₄₀S₃₀Se₂₀ film is reported in this paper. The film shows an optical non-linear response of 200 fs under ultrafast 80 fs-pulse excitation, and the values of real and imaginary parts of non-linear susceptibility χ⁽³⁾ were 9.0×10⁻¹² and −4.0×10⁻¹² esu, respectively. The large third-order non-linearity and ultrafast response are attributed to the ultrafast distortion of the electron orbits surrounding the average positions of the nucleus of Ge, As, S and Se atoms. This Ge₁₀As₄₀S₃₀Se₂₀ chalcogenide glass would be expected as a promising material for optical switching technique.     

Study of the dynamics and mechanisms of deformation of thin chalcogenide As(Ge)<Subscript>2</Subscript>Se<Subscript>3</Subscript> films by nanoindentation

The mechanical properties of As₂Se₃ and Ge₂Se₃ thin films have been studied by the method of quasi-static nonoindentation. The mechanisms of formation and recovery of the indentations in the studied materials have been analyzed under conditions of their local loading. It has been revealed that the deformation mechanism of the chalcogenide films changes in going from As₂Se₃ to Ge₂Se₃. It has been found that, during deformation of the As₂Se₃ film under the indenter, the accumulation of plastic deformation prevails, and, for the Ge₂Se₃ film, the substantial mechanism is the relaxation of its deformation.     

Crystallization kinetics in new Sb14As29Se52Te5 amorphous glass

Differential scanning calorimetry (DSC) under non-isothermal conditions is used to study the crystallization kinetics of Sb₁₄As₂₉Se₅₂Te₅ chalcogenide glass. In addition, two approaches are used to analyze the dependence of glass transition temperature (T_g) on the heating rate (α). One is empirical linear relationship between (T_g) and ln(α). The second approach is the use of straight line vs. 1/T_g for the evaluation of the activation energy for glass transition. The phases at which the alloy crystallizes after the thermal treatment have been identified by using X-ray diffraction. The diffractogram of the transformed material shows the presence of some crystallites of As, Te, AsSb, As₂Se₃, Sb₂Se₃ and AsSe_.5Te_.5 in the residual amorphous matrix.     

Variation of Raman spectrum after optical excitation in amorphous As2Se3 at 1.6°K

Several experiments, involving electronic states have shown that amorphous As₂Se₃ is modified at low temperature by the action of not very strongly absorbed light (α～10²cm^?1). This paper presents Raman scattering results before and after illumination. The shape of the Raman spectrum is changed by illumination: its high energy side has grown near 260 cm^?1. This light induced modification of the vibrational states is discussed within the framework of a previous qualitative model involving changes in local atomic configuration.